For a post-travel headache and vomiting, dehydration or motion sickness is the likely cause. First, slowly sip oral rehydration salts (ORS) or water. For the headache, Paracetamol (Acetaminophen) is a safe option; avoid Ibuprofen if your stomach is highly irritated. For vomiting, over-the-counter motion sickness medications like Meclizine can help, but prescription antiemetics like Ondansetron are more effective. Rest in a dark, quiet room. If you cannot keep any fluids down or if the headache becomes severe, please seek immediate medical attention.